China
Africa
Explore chapters and articles related to this topic
Testing and Analysis of Blended Lubricants
Published in R. David Whitby, Lubricant Blending and Quality Assurance, 2018
Fatigue wear occurs under certain conditions when the lubricating oil film is intact and metallic contact of opposing asperities is either nil or relatively small. Cyclic stressing of the surfaces causes fatigue cracks to form in the metal, leading to fatigue spalling or pitting. Fatigue wear occurs in rolling element bearings and gears when there is a high degree of rolling, and adhesive wear, associated with sliding, is negligible. A variation of the fatigue pitting wear is the micropitting wear mechanism that results in small pits in the surfaces of some gears and bearings. Asperity interaction and high loads as well as metallurgy are factors influencing micropitting. An upgraded version of the standard FZG spur gear tester is used to evaluate gear oil micropitting performance according to a German Research Institute test method called FVA (Forschungsvereinigung Antriebstechnik) Method 54.
Wear
Published in Kenneth C. Ludema, Oyelayo O. Ajayi, Friction, Wear, Lubrication, 2018
Kenneth C. Ludema, Oyelayo O. Ajayi
This is wear mode seen primarily in surfaces of components involved in rolling and rolling/sliding contact. These include rolling element bearings, gears, railway tracks. Pitting often occurs at different scales. When the pitting is large enough, order of contact area, it is often termed macropitting. If the pitting is at a much smaller scale, order of surface asperity, it is termed micropitting. Regardless of the scale, the root cause of pitting is contact fatigue. For a non-conformal rolling Hertzian contact, the stresses in the material during a load passage are schematically shown in Figure 9.22. The material is subjected to stress pulses consisting of shear stress τxz which undergoes complete reversal and σx and σz, both compressive.
Lubricating Oils
Published in Don M. Pirro, Martin Webster, Ekkehard Daschner, Lubrication Fundamentals, 2017
Don M. Pirro, Martin Webster, Ekkehard Daschner
Fatigue wear occurs under certain conditions where the lubricating oil film is intact and metallic contact of opposing asperities is either nonexistent or is relatively small. Because of cyclic stressing of the surfaces, fatigue cracks form in the metal and lead to fatigue spalling or pitting. Fatigue wear occurs in rolling element bearings and gears where there is a high degree of rolling and where adhesive wear associated with sliding is negligible. A variation of the fatigue pitting wear is the micropitting wear mechanism that results in small pits in the surfaces of some gears and bearings. Asperity interaction and high loads as well as metallurgy are factors influencing micropitting. An upgraded version of the standard FZG Spur Gear Tester is used to evaluate gear oil micropitting performance according to the Forschungsvereinigung Antriebstechnik (FVA) Method NR 54.
A comprehensive study on multi-objective design optimization of spur gear
Published in Mechanics Based Design of Structures and Machines, 2023
In geared transmission systems, fluctuation of load and speed leads to alteration in lubrication condition. Partial and boundary lubrication region along the path of contact results in initiation of micro-pitting due to contact fatigue. This prevailing condition may result in the formation of other types of wear like spalling, scoring and scuffing (Glodez et al. 1997; Hohn and Michaelis 2004).